Back head construction for rock drills



July 26, 1932. G. M. NELL 6 BACK HEAD CONSTRUCTION FOR ROCK DRILLS Filed July 15. 1930 2 Sheets-Sheet 1 INVENTOR. v Q/sfm/e M /Ve// A TTORNE Y.

July 26, 1932. G. M. NELL 1,853,670

' BACK HEAD CONSTRUCTIOH FUR ROCK DRILLS Filed July 15,1930 z'sheets-sneen 2 I N VEN TOR. Qusfave M /V;//

VZMJM A TTORNE Y.

Patented July 26, 1932 I UNITED S TES GUSTAVE PA ENT 1 BACK HEAD oonscrnncmxon ron nocx mums Application filed Ju1y 1 5,

.This invention relates to fluid pressure perc'ussivetools for rock drilling and similar operations, especially of the" type having a tube extending axially thereof for passing 'sfiuid, either air or waterinto the drill hole to clear the same and/onto allay dust. More particularly it concerns the back headconstruction for such tools. I p

In conventional rock drllls utlhzing, a cen- 1o tral fluid tube with a screw plug holding the same in place; it frequently happens that the threads on the plug wear out or strip before the balance of the back head is worn out. In such. a case much difficulty is expei'sriencedin rebushing theback head in accord v p p I lubrlcant reservolr 7 a which feeds into the ance with'the usual practice and thebu'shing readily becomes loose."

One object of the invention is to provide an improved back head and bushing struc- 29 ture for tools of the described type. An

other object is to hold' the bushing securely in place but to make it readily renewable. Another object is to utilize the bushing to rovide a fluid. chamber or reservoir in the ack head. Other objects willappear from o the detailed description which follows. i

In order to illustrate the invention concrete embodiments thereof are shown in the accompanying drawings, in which: 'Fig. 1 is a sectional View of a fragmentary portion of a liuid pressure drill having rotation' mechanism and provided with a baclr head having handles for hand sinking;

Fig. 2 is a top plan view of the parts shown in Fig. 1 with one 'ofthe handles broken p k x p or projection 03 on rifle bar D.

In the form of the invention shown in Figs. 1130 3, the drilling machine comprises a cylinder A in which reciprocates a hammer piston 13, the machine being provided with conventional rotation mechanism for stepping piston B around during at least apart 7 70. Handle'8 serves as a conduit for the moj Fig. {is a longitudinal sectional View of p 1930. Serial ,;4es,071.

of its" reciprocatory movement; i such mech- FFICE,

MLN LL, or DETROIT, MICHIGAN, AssIGNoaTo CHICAGO PNEUMATICTOOL;

COMPANY, or NEW-YORK, N. Y.,- A CORPORATION. on NEW ERSEY anism may comprise a rifle nut C mounted in v a recess in the piston to receive a rifle bar D which projects. through and hasa bearingjin a cylinder ring E and'has ratchet mechanisnr including a ratchet ring securediinasocket or recess therefor in thebackhead.

The backhead 6, to which the inventionparticularly relates, servesas a iclosure for the rear endof cylinder A' and is secured thereto in any suitable manner" as hymn-1 ventional through bolts or side-rods G"(Fig." 2'). As shown it has'opposed handles 7:.and 8 for manually supporting the drill, both handles 'being h'ollow, handle 7 providinga drill through restricted passage/7b and is. filled through an end opening closed by plug tive fi uidadmitted theieto'th'rough the plug connection 8a and may have. a throttlefvalve 8b of'any suitable or desired type witha manually actuated handle arranged conven iently adjacentsupporting handle 8. a \Backhead '6 has a bushing 9 therewithin having two diametersqproviding a tight press 'fit atlO and 11 with cooperatingbores in the back head; Diameter ,11 is' greater than diameter 10 thereby forming" a stop 7 flange 12 OIlbIlSl'iiIlgQ positively to limit the inward projection of the bushing when inrectly in line withthe' piston chamber and haisfa' recess 18 formingla. bearing foraboss Bushing 9 is reduced intermediate Idiani I v ter-10 and flange 12 and back'head dis' ref cessed or undercut atithis point to prov de an annular chamber 14 of substantial capace 75 "insertable from the cylinder side thereof'and I serted. As shown, bushing 9 is disposed di ity, which in the present instanoe'is'utilized I for motive fluidland provides for unrestrict ed flow ofthesame'to .a down passageld adjacent the plug forming the restricted lubricant passage/7b and thence to. suita'ble means (not shown) for distributing the I sameto reciprocate piston B.

In the event that the percussivetobl is provided' with a central fiuid tubeH for hole cleaning, bushing Qhas a restricted bore "16 axially aligned and concentric with recess 13 for tube H and an enlarged bore or cavity 17. Bore 17 is screw-threaded for a plug 18 which with gasket 19 and washer 20 form a conventional method of holding the tube in place. An outer cap 21 is secured by threaded engagement to the exterior of plug 18 in accordance with the usual practice and receives water and/or motive fluid through a passage 22 (Fig. 2). On account of the excessive force which is frequently applied to plug 18 to secure a tight seal around tube H, and especially when there are ports through bushing 9 which must match *ith the back head, it is advisable to provide a positive step against relative movement in any axially rotative direction. Such a stop may take the form of a pin 23 (Figs. 2 and 3) which is secured in back head 6 adjacent diameter 11 and cooperates with a recess 24 in flange 12 on bushing 9.

Ratchet ring F of the rotation mechanism may be mounted in back head 6 in any suitable or desired manner which will prevent turning of the same and may be utilized to maintain bushing 9 against loosening. By preference ring is threaded 0n the outside as indicated and in such a manner that the rotational reaction of the impulses transmitted by the ratchet and pawl mechanism for rifle bar D will cause ratchet ring F to screw outwardly and tightly against bushing 9, thereby securely clamping and holding the latter in place.

In the embodiment of the invention shown in Figs. 4 and 5, there is variation in certain minor details in the back head construction but the principal features remain the same. Fig. 4 shows in longitudinal section all the parts of a percussive drill and the same reference characters used in Fig. 1 are here applied without repeating the description of the same. As for the additional parts, the splined extension of piston 13 has a bearing in bushing I and co-operates with a splined nut J carried by a rotary sleeve K. Cylinder bushing L telescoped within cylinder A and having a. flange interposed be tween the latter and front head M rotatably supports sleeve K. Front head M through bushing N rotatably supports chuck O suitably keyed by a splined or similar connection to sleeve L. Chuck 0 receives the polygonal shank of a hollow drill steel P which is stepped around by the rotation mechanism of the drill and receives the blows of piston B through an interposed anvil block R slidably mounted in sleeve K.

Back head 6a receives bushing 9a. with a tight press fit at diameters 10a and 11a. Diameter 10a is the smaller and adjacent the same bushing 9 has a flange 12a serving as a. positive stop. A pin 23a keys these parts against relative movement. Bushing 9a is reduced intermediate stop flange 12a and diame-ter 11a and back head 6a is recessed or undercut at the same point to provide an annular fluid chamber 14a of large capacity, which in the present instance is used for lubricant and is arranged to be filled when necessary through an opening closed by plug 27. Lubricant passages 28 and 29, partly in back head 6a and partly in bushing 9a, lead from opposite sides of lubricant chamber 14a to plugs 30 and 31 in bushing 9a which have restricted openings 30a and 31a leading to the recess in back head 6a for the ratchet mechanism including ratchet ring F. This lubricant feeding arrangement serves a double purpose due to the fact that, when the oil level in chamber 14a is below passage 28 and manually operated throttle valve 32 is closed so that the motive fiuid pressure drops to atmosphere through passage 33 in ratchet ring E and the piston chamber, port 30a in plug 30 will oiler less resistance to the passage of air than to oil and the pressure in oil reservoir 14a above the oil level will find a ready means of egress. This prevents a large part of the oil from being forced out of the reservoir every time the throttle is closed but a certain small amount will be ejected. It

frequently happens in mining that a machine of the type shown in Fig. 4 is mounted under the supporting column arm in an upsidedown position from the normal position here shown and in that event the respective functions of plugs 30 and 31 will be automatically reversed.

Lubricant passage 33 provides for movement of lubricant to the moving parts of the percussive motor. To utilize lubricant from reservoir 14a also for the moving parts of the rotation train at the forward end of the machine, a minute leak is provided at 34 between ratchet rin F and cylinder ring E from which leads a short passage 35 to an axial passage 36 with branches 37, 38 and 39 to the parts requiring lubrication. A constant stream of motive fluid enters passage 36 from a port 32a in throttle valve 32 when the drilling machine is in operation. To secure seepage of oil at 34 the length of ratchet ring F may be made slightly less than the depth of the back head socket therefor in back head 6a. Only a very slight clearance is required as of the order of .0005 inch. Passage 36 opens to the front of the machine and is normally under less air pressure than obtains in the ratchet chamber from the pulsations of live air reaching the same from the rear end of the piston chamber through passage 33. Whenever the air pressure is higher in the ratchet and pawl chamber than in passage 36 a small amount of lubricant will be forced through the clearance at 34 and thence through passage 35 into axial passage 36. It is obvious that the lubricant cannot be forced back again through the slight clearance at 34 even though the pressure in axial passage 36 should momentarily rise higher than in the ratchet chamber.

Renewable back head bushing 9ais similar to bushing 9 of the first embodiment (Figs 1, 2 and 3) in that it provides a bearing recess 40 for extension (Z of rifle bar D, a bore 41 for axial tube H and a threaded socket for plug 42 acting through gasket 43 and washer 44 securely to hold the tube in place. A cap 45 threadedlyengages the exterior of plug 42. a

From the above it will be apparent that each of the back head structures herein shown will effect economies in the upkeep of fluid pressure drilling machines of the described type since it provides a conveniently renew able bushing with means for supporting the axially disposed fluid tube and since it also provides a renewable bearing for the end of the rifle bar. The bushing further cooperates with the back head to provide a fluid chamber which may be used, as in the embodiment shown in Figs. 1 to 3, for an unrestricted passage for motive fluid or, as in the embodiment shown in Fig. 4, for a lubricant reservoir of substantial size. The backhead and the bushing may be further arranged as indicated in the form shown mFlg. a with connections to the moving parts for both percussion and rotation so as to adequately lubricate the same regardless of the position of the a machine and without waste of lubricant when.

the throttle valve is closed. In short the present invention overcomes many of the difiiculties encountered with back heads of the prior art by providing the ba ck head initially with a bushing which is easily renewable and which is held tightly inplaceeither as a re-' sult of the assembly of the partsor by 'reaction from the operation of the machine.

While the invention has been herein shown and described in what are now considered to be preferred forms, it is to be understood that the invention is not restricted to the specific details thereof but covers all changes, modifications, and adaptations within the scope of the appended claims.

I claim as my invention 1. In a fluid pressure percussive tool having rotation mechanism for the working tool including a ratchet ring, a rear cylinder closure member, a centrally located bushing against longitudinalmovement. I

. 8.r1In.a fluid pressure percussive tool having rotation mechanism romprismg a rifle bar and ratchet' meansincluding a ratchet said-rifle bar to I hold said bushing member ring, arear cylinder closure enclosing said ratchet means, acentrally located bushing member .withinsaid closuremember, said ratchet ring having threaded engagement with said closure and being in abutting relation with said bushing member, the reaction of said rotation mechanism, on said ratchet ring being" utilized 1 to tighten the latter against said bushing,

4:..Ina fluid pressure percussive tool hav; ing rotation mechanism comprising a rifle barand' ratchet means including a ratchet ring, a rear cylinder closure enclosingsaid ratchet means, a centrally located bushing memberfwithin said closure member, prov'idingabearing for the rear end of said rifle bar, said ratchet ringhaving threaded en gagement with said closure and being in abutblows .toa drill steel, rotary chuck means at the forward end of said: cylinder supporting saiddrill steel, aback head for said cylinder,v

d to tightenthelatter against said bushing. i e

a riflebarihaving ratchetand pawl mechar I nism including a ratchet ring mounted in said backshead,-a bushing in said back head 'providing a-bearing for said iriflefbarand co-, operating with said back head to provide a lub'ricantv: chamber within the latter, said ratchet ring having-threaded engagement 7 with, said back 1 head. and abutting 1 contact with said-bushing whereby the reaction of saidrifle bar is utilized to tighten said ratchet ring 'againstis'aid bushing securely to clamp thelatterlin place, means for feeding lubricant in restricted amount in 'a'plurality of positions of said tool to said ratchet and pawl mechanism and thence to said cylinder, said cylinder having a passage extending to said rotary chuck means,1ineans providing for seepage of lubricant to said passage including slightclearance adjacent said ratchet ring, and means supplying motive fluid 'to said passage to carry the seeping lubricant to 7 said rotary chuck means. i g y 6. A fluid pressure tool having acylinder and mechanism for imparting percussion and rotation to a hollow drill steel, a tube for conducting fluid axially through said tool to the interior ofs'aid steel, a back head for said cylinder, and a renewable bushing in said back head providing a bearing for a portion of said mechanism and means for securely c mounting said tube, spacedportions of said back headand bushing member-engaging one another with a pressfit and providing therebetween and within said closure a" lubricant chamber, and means including restricted connections to spaced parts of said chamber for effecting movement of lubricant to the moving parts of the tool but relieving the pressure in said chamber to avoid waste of lubricant when the tool is not operating.

7. A fluid pressure tool having a cylinder, a piston reciprocable therein for imparting blows to a drill steel, rotary chuck means at the forward end of said cylinder supporting said drill steel, a back head for said cylinder, a rifle bar having ratchet and pawl mechanism including a ratchet ring mounted in said back head, a bushing in said back head providing a bearing for said rifle bar and cooperating with said back head to provide a lubricant chamber within the latter, means for feeding lubricant from said chamber to said ratchet and pawl mechanism and thence into said cylinder, said cylinder having a passage extending to said rotary chuck means, and means providing for seepage of lubricant to said passage.

8; A fluid pressure tool having a cylinder, a piston reciprocable therein for imparting blows to a drill steel, rotary chuck means at the forward end of said cylinder supporting said drill steel, a back head for said cylinder, a rifle bar having ratchet and pawl mechanism including a ratchet ring mounted in said back head, a bushing in said back head providing a bearing for said rifle bar and co operating with said back head to provide a lubricant chamber within the latter, means for feeding lubricant in restricted amount in a plurality of positions of said tool to said ratchet and pawl mechanism and thence to said cylinder, said cylinder having a passage extending to said rotary chuck means, means providing for seepage of lubricant to said passage including slight clearance adjacent said ratchet ring, and means supplying motive fluid to said passage to carry the seeping lubricant to said rotary chuck means.

Signed by me at Detroit, in the county of Wayne and State of Michigan, this 8 day of July, 1930.

GUSTAVE M. NELL. 

